Display screen or portion thereof with a graphical user interface



The FIGURE is a front view of a display screen or portion thereof with agraphical user interface showing our new design.

In the FIGURE, the outer broken lines show a display screen or a portionthereof that form no part of the claimed design. The other broken linesshow portions of the graphical user interface that form no part of theclaimed design.

CLAIM The ornamental design for a display screen or portion thereof witha graphical user interface, as shown and described.